It has long been known that alcohol can react with ammonia or primary or secondary amines to replace one or more hydrogen atoms bonded to nitrogen with the alkyl residue of the alcohol. The reaction is promoted by catalysts. Use of a supported oxygen compound of phosphorus is reported in U. S. 2,073,671. Another process is described in U. S. 2,160,058 using copper-barium-chromium oxides, copper-chromium oxides or copper-aluminum oxides. Reaction of ethylene glycol with ammonia using a catalyst such as nickel-aluminum, nickel-silicon, nickel, copper, copper-chromium, copper-zinc-chromium, thorium, magnesium, molybdenum or osmium oxides is said to form alkoxy amines according to U. S. 2,160,058. Reaction of an alcohol with ammonia or an amine in the presence of hydrogen using an alumina or silica supported cobalt-nickel-copper-catalyst is described in U.S. 4,014,933. Hoshino et al. U. S. 4,210,605 describe a process for making aliphatic amines by reacting an aliphatic alcohol or aldehyde with ammonia or a primary or secondary amine using a homogenous colloidal catalyst formed by dissolving a copper or silver salt of a fatty acid in alcohol and reducing the metal. Optionally the solution can contain a Group VIII metal carboxylate or a manganese or zinc metal carboxylate. It can also contain an alkali metal or alkaline earth metal carboxylate. The catalyst formed is a homogenous colloid that cannot be separated by filtration. In contrast the present catalyst is a solid catalyst that can be removed by filtration and recycled.
More recently, U. S. 4,409,399 describes the alkylation of ammonia or a primary or secondary amine using as the catalyst an unsupported copper oxide or hydroxide, nickel oxide or hydroxide and optionally a Group IIA metal oxide or hydroxide. Similarly Blackhurst U. S. 4,683,336 describes an amination process which uses a copper carbonate-nickel carbonate catalyst which may optionally contain cobalt carbonate.
One of the problems encountered when making long-chain alkyl di-lower alkylamines such as C.sub.8-22 alkyl dimethylamines by the reaction of a long-chain alcohol with a di-lower alkylamine is that any unreacted long-chain alcohol remaining in the reaction mixture will boil at about the same temperature as the desired product which makes purification very difficult. Hence, it is essential that conversion of alcohol be essentially complete, e.g., at least 95%, to have a commercially viable process when making an amine such as a C.sub.8-22 alkyl dimethylamine. Likewise it is essential that disproportionation to form long-chain alkylamine and/or long-chain alkyl mono-lower alkylamine be minimized as these primary and secondary amines are also extremely difficult to separate from the desired long-chain alkyl di-lower alkylamine product.
Another problem with the catalytic route to trialkylamine is that such processes can form by-products such as alkanamides of the amines and alkyl alkanoate esters from the alcohol. Also when attempting to make a long-chain alkyl dilower-alkylamine, alkyl interchange can occur to give di-long-chain alkyl mono-lower alkylamine. These reactions lower the yield and also form by-products having a high molecular weight such that they remain in the trialkylamine products unless the entire product is rectified and even then separation can be difficult.